A conventional image forming apparatus, such as a copying machine, a printer, and a facsimile apparatus, employs an electrophotographic method. During image forming, the electrophotographic type image forming apparatus applies a high voltage to a developing member configured to develop a latent image that has been formed on an image bearing member by using a toner, which is a developer, to a charging member that evenly charges the image bearing member, and to a transfer member that transfers the toner image that has been formed on the image bearing member onto to recording material.
As a high-voltage power source that outputs a high voltage to a plurality of members used during image forming, a high-voltage power so time that uses a winding type electromagnetic transformer is used. For example, Japanese Patent Application Laid-Open No. 06-309044 discusses a high-voltage power source that uses an electromagnetic transformer.
FIG. 7 illustrates an example of a high-voltage power source that outputs bipolar high voltages by using two electromagnetic transformers. Referring to FIG. 7, a high-voltage power source 713, which outputs a negative voltage, includes an electromagnetic transformer 701.
The electromagnetic transformer 701 generates an alternating current (AC) high voltage on a secondary winding with AC power applied to a transformer primary winding via a primary drive circuit 705 for the electromagnetic transformer 701, which includes a switching element. The AC high voltage generated on the secondary winding is rectified and smoothed by a diode 702 and a capacitor 703 to be output as a negative direct current (DC) voltage. In addition, the negative high-voltage power source 713 includes a bleeder resistor 704.
On the other hand, a high-voltage power source 712, which generates a positive voltage, includes an electromagnetic transformer 706 similar to the negative-voltage high-voltage power source 713. The high-voltage power source 712 generates an AC high voltage on the secondary winding with AC power applied to a primary winding of the electromagnetic transformer 706 via a primary drive circuit 710.
The generated AC high voltage is rectified and smoothed by a diode 707 and high-voltage capacitor 708 to be output as a positive DC high voltage. In addition, the positive high-voltage power source 712 includes a bleeder resistor 709.
The negative high-voltage power source 713 and the positive voltage high-voltage power source 712 are serially connected. The DC high voltage that has been generated by each high-voltage power source is applied to a load 711 via the bleeder resistor 704 or 709. In addition, the negative high-voltage power source 713 includes a current detection circuit 714.
In recent years, it is desired by the market that an image forming apparatus be as small-sized and lightweight as possible and can be manufactured with low costs. In this order, it becomes necessary to reduce the size, the weight, and the costs of a high-voltage power source mounted on the image forming apparatus.
In reducing the size, the weight, and the costs of the high-voltage power source illustrated in FIG. 7, which uses an electromagnetic transformer, the following issue may arise. Generally, the height (vertical dimension) and the volume of an electromagnetic transformer are larger than those of other electronic components. Accordingly, in further reducing the size of a high-voltage power source, it is important to reduce the size of the electromagnetic transformer.
Because an electromagnetic transformer outputs a necessarily high voltage as described above, it is required to provide a winding of a number of windings greater than a predetermined number. Accordingly, the size of an electromagnetic transformer configured to output a high voltage may not be easily reduced.
In general, a ferrite electromagnetic transformer or a copper electromagnetic transformer is widely used. Accordingly, the electromagnetic transformer like this is heavier than other electronic components. Accordingly, the weight of a high-voltage power source may not be easily reduced. In addition, because the electromagnetic transformer is made of ferrite or copper, the costs for manufacturing, the electromagnetic transformer may become higher than the costs for manufacturing other electronic components. Accordingly, the costs for the high-voltage power source may not be easily reduced due to the high costs for the electromagnetic transformer.
As described above, a further reduction of the size, the weight, and the costs for the high-voltage power source using an electromagnetic transformer is limited. In other words, in further reducing the size, the weight, and the costs of an image forming apparatus including a plurality of high-voltage, power sources, the size, the weight, and the costs of the high-voltage power sources may be the issue.